**We have seen Star and delta connection is Transformers. Now Star into delta conversions allows us to convert impedances connected together from one type of connections to another. This conversion can be done by using Kirchoff’s circuit laws.**

*Star to Delta Conversion***I**n three phase power supply Star to delta conversion can be done easily by using these transformations.

Circuit for the conversion is as shown below:-

There are following
formula used for conversion for Star to delta.

Resistance RA=

__R1R2 + R2R3 + R3R1__……………… (i)
R3

Resistance RB=

__R1R2 + R2R3 + R3R1__……………… (ii)
R2

Resistance RC=

__R1R2 + R2R3 + R3R1__……………… (iii)
R1

*Delta to Star Conversion*
Now you see from above
formula when there is need to calculate equivalent resistance in delta
connection while conversion from Star connections is sum of product of every
two branch resistances in star connections divided by resistance if opposite
branch. From equation (i) you see that while calculating resistance in delta
across branch RA then this will be equal to sum of product of two branches
divided by resistance of opposite node. Similarly resistance value of other
branches can be calculated.

Diagram for conversion from Delta to Star is as below:-

Now let’s see when
there is conversion from Delta to Star then following formula can be used:-

Resistance R1=

__RA RB__……………………………..(a)__`__RA+RB+RC

Resistance R2=

__RA RC__……………………………..(b)
RA+RB+RC

Resistance R3=

__RB RC__……………………………..(c)
RA+RB+RC

Now from above we can see that while conversion from
delta to star connections resistance of branch which is under calculation is equal to product
of two branches which are connected to Node divided by Sum of resistances of
all branches .

From equation 1 we have seen that while calculating resistance
across branch RA , resistance will be product of resistances connected to node1
while in delta divided by sum of resistances in all branches.

From above you can see that it will be easy to convert
star into delta and delta into star by using these formula’s. This conversion
is used to analyze the circuits. These transformations are applicable for both
resistance and impedances.

These Transformations are used to solve complex circuits.